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        <td class="header"> Cross InSAR Resampling</td>
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<h3>Cross Interferometry Resampling</h3>

<p>
    This operator prepares input, ERS1/2 and Envisat, data for cross interferometric processing. The input image is 
    resampled to the requested geometry. For example, for Cross InSAR, with ERS image as a master Envisat ASAR image 
    should be resampled into the geometry of ERS to allow reliable corregistration.  
</p>

<h4>Operator Parameters</h4>

<p>
    The following parameters are used by this operator:</p>

<ul>
    <li>
        <b>Interpolation Polynomial Degree:</b> Degree of two-dimensional polynomial. Degree 2 is advised.
    </li>
    <li>
        <b>Interpolation Method:</b> List of interpolation kernels.
    </li>
    <li>
        <b>Target Geometry:</b> List of target geometry. For example, to resample ERS to ASAR geometry, select ASAR.
    </li>
</ul>
    
<h4>Important Usability Note</h4>

<p>This operator is designed and implemented having having in mind data acquired during dedicated ERS2 - Envisat 
    Tandem Campaigns. For successful computation of Cross InSAR interferograms, between ERS/Envisat data, a 
    perpendicular baseline of approximately 2km is required. For the regular smaller baselines the results will be
    suboptimal, if not completely decorrelated.
</p>


<h4>Implementation Details</h4>

<p>
    Basically this operator performs estimation of the resampling polynomial, and resampling of input image from the 
    source into the target geometry using a deterministic relationship between source/target geometries. In this 
    case, this deterministic, relationship is defined by ratios of azimuth resolution (governed by 
    Pulse Repetition Frequency (PRF)) and range resolution (governed by Range Sampling Rate (RSR)) - see Figure 1. 
    Ratios between source and target resolution is used to compute a deterministic offsets between geometries, 
    than these offsets are used to compute polynomial and resample geometries.
</p>

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<div style="margin-left: 35px;"><img style="" alt="" src="../images/ers_envisat_ratios.jpg"></div>
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<div style="margin-left: 20px;"><b>Figure 1.</b> Ratio between Envisat ASAR and ERS 1/2 SAR geometries.<br></div>

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